THE CARDONIFEROUS FLORA. 



107 



dinally riMtcd und jointed stoms so frcr|iient in tho eoal-fommtion, 

 and of which tlic coinrnon ('. Suckorii is a tyiticiil form. 'I'hc most 

 perfoct of these stfiiiH n-preseiit the outer siirfjice iinniediateiy witliin 

 the epiflerinis, in which case transvor«o lines or constrietions 

 mark the nodes, anrl at tho nodes there are ronnded spots, some- 

 times indi(!(ilin;^ nidiiil processes of the i)ith, first dcst^ribed by 

 Williamson ; in other cases, the attachment of hranchlels, or in some 

 specimens both. Hut some specimens show the outer surface of tho 

 opirlermis, in which case tho transverse nodal lines are usually in- 

 visible, tliou^^h the scars f)f brurichlets may appear. Iti still other 

 examples the whole of the outer tissu(!S have perished, and the so- 

 cailetl Calamite is a cast of the interior of the stem, showing merely 

 longitudinal ribi>inj,' and transverse nodal constrictions. In study- 

 ing' these plants in m'tu in the erect Calamite brakes of the coal- 

 foririation of Nova Scotia, one soon becomes familiar with these ap- 

 pearances, but th(!y are evidently unknown to the majority of palajo- 

 botanists, though described in detail more than twenty years ago. 



When th(! outer surfa(;e is preserved it is sometinu's seen to bear 

 vcrti(;ils of iutig nee(ll(!-lik(! leaves (C. (Jift/ii), or of branchlets with 

 secondary whorls of similar leaves {(J. Suclcovii and C. rmdidatuH), 

 No ('alamito known to mo bears broad one-nerved leaves like those 

 of Aiit''rop/n///i/t'fi iiiul Annuhirid, though the larger stems of these 

 plants have been described as Calauiitcs, and the term ('alftmoclatlus 

 has been used to includt; both groups. The base of the ('alamito 

 stem usually tcrminat(!S in a blunt point, and may be attached to a 

 rhizome, or sevc^ral steins may bud out from each other in a group or 

 stool. Tho roots are long and cylindrical, sometimes branching. 

 The fruit consists of spikes of spore-cases, borne in whorls and sub- 

 t(!nded by linear floral leaves. To these strobiles tho name Calamo- 

 stachys has been given. 



Williamson has shown that the stem of Calamitcs consists of a 

 central pith or cavity of large size surroutided by a cylinder con- 

 sisting of alternato wedges ot woody and cellular matter, with ver- 

 tical canals at the iimer sides of tlu; wedges, and slender medullary 

 rays. The thick cellular wedges intervening between the woody 

 wedges he calls [irimary medullary rays; the smaller medullary 

 rays in the wedges, secondary medullary rays. There is thus a 

 highly complex exogenous stem based on the same principle with 

 the stem of a common Equiadum, but with much greater strength 

 and complexity. 



Williamson has also shown that there are different sub-tyi)es of 

 these stems. More especially he refers to the three following: 



